The present invention relates to a method and a device for assisting a driver of a vehicle, said vehicle having an engine and a braking system, an accelerator that conveys the driver""s wishes concerning acceleration to the engine, and a brake pedal that conveys the driver""s wishes concerning retardation to the braking system.
The method in accordance with the invention comprises the steps of, taking into consideration several factors, such as a division of a specific driving distance into shorter segments, determining a speed profile for the driving distance, which speed profile comprises a relation between a speed set point and position, and regularly reading the current speed set point from the speed profile.
The automatic control of vehicles, particularly commercial vehicles such as buses, has been studied with the objective of minimising emission from vehicles and minimising energy consumption. In the article entitled xe2x80x9cControl strategies for an electric Hybrid bus adapted to a specific routexe2x80x9d, by Jan Andersson, Roger Axelsson and Bengt Jacobsson, presented at AVEC1998, the concept of xe2x80x9cadvisorxe2x80x9d was introduced. This xe2x80x9cadvisorxe2x80x9d, which constitutes a part of the control system of the vehicle, calculates a suitable speed profile on the basis of the planned route of the vehicle, i.e. the speed the vehicle should keep at each moment of the journey. The advisor regularly receives data as to the speed and position of the vehicle and the current time, in order to update the speed profile.
This speed profile shall then influence the driver with a view to achieving smoother driving and thus a more optimal energy consumption and level of emission. In the article mentioned above the advisor influences the control system for the vehicle""s engine directly. The actions of the driver in depressing or releasing the accelerator and brake pedals are regarded as input signals to the advisor, which thus acts as a kind of filter.
This entails a possible traffic danger for two reasons. In the first place the driver does not have sufficiently direct contact with the control system of the vehicle. The advisor, which in a mathematical model follows the behaviour of the driver, can hardly be prepared for all human behaviour. xe2x80x9cMisunderstandingsxe2x80x9d may consequently arise between driver and advisor. In the second place there is a risk of the driver being lulled into playing an all too passive part since an advisor constantly supervises his behaviour.
One problem with the use of such an advisor is to activate the driver sufficiently so that his driving behaviour will be changed without causing a traffic danger due to the driver becoming too passive.
The object of the present invention is to solve the above problem and provide a method and a device for assisting a driver of a vehicle, such as a bus, to promote a smoother style of driving with lower levels of emission and lower fuel consumption.
Another object of the invention is to further develop the concept of an xe2x80x9cadvisorxe2x80x9d, as mentioned above, and to implement this concept in a vehicle.
To achieve the above objects the invention provides a method of the type described above, characterised by the steps of controlling the engine and the braking system on the basis of the speed set point, by means of at least one actuator influencing the accelerator or braking pedal of the vehicle in accordance with said control, determining whether the driver is applying a force on one of the pedals that is greater than a predetermined threshold value and, if such is the case, allowing the driver to override the influence of the actuator.
The method in accordance with the invention enables a vehicle to be controlled in accordance with an optimal speed profile in order to minimise emission and fuel consumption. At the same time the driver is given information as to the signals transmitted to the engine and braking system by the regulator. If the driver deems it necessary he can override the system, but only by applying sufficient force on the pedals. This force is determined to a suitable magnitude by means of tests depending, for instance, on the strength of the driver.
The force applied by the driver on a pedal may be determined by the pedal being movable against the action of a spring force, and a sensor determining when the pedal has been moved a specific distance. The force applied by the driver on a pedal may also be determined by a piezoelectric element.
The information utilised by the method is in the first placed related to the relevant distance to be driven, which is suitably divided into segments, each segment being associated with a number of factors related to road conditions and speed limits, for instance, and to the time table and planned stops along the route.
This information is entirely independent of the vehicle and may be included in a common information package tied to a specific route.
Secondly, the method utilises information related to the capabilities of the vehicle, such as engine power, transmission, inertia, etc. This information is similarly entirely independent of the route and may be included in an information package tied to a specific type of vehicle.
Thirdly, the method utilises continuous information from the internal data system of the vehicle, such as speed, position and time. This information is already used in modern public transport vehicles and no technical problems are entailed in obtaining it.
The step of controlling the engine and the braking system on the basis of the speed set point can be performed by direct activation of the accelerator and the brake pedal. This gives a particularly clear coupling between the control of the engine and braking system on the one hand, and the position of the pedals on the other hand.
In accordance with the invention a device is also provided for performing the method.